1. Field of the Invention
The present invention relates to an original guiding device having an original conveying path formed along the upper surface of a transparent platen and a reading optical system fixed below the transparent platen, and adaptable to an image reading device for reading an original by the reading optical system while conveying the original through the original conveying path.
2. Description of Related Art
In a digital copying machine, a facsimile, or an image reader, for example, an image reading device for reading an image of an original moved along the upper surface of a transparent platen by an optical system fixed below the transparent platen may, in some cases, be used. An arrangement of an original conveying device used for such an image reading device in the vicinity of the transparent platen is shown in FIGS. 6 and 7.
An original holding member 28 is provided in a state where a clearance defining an original conveying path 29 is ensured above a transparent platen 21. An original P to be read is fed to the original conveying path 29 through an original carrying-in path 27 curved in an approximately C shape, as viewed from the front, from an original tray (not shown) arranged diagonally to the upper right in the drawing of the transparent platen 21. That is, the original P is fed to the original conveying path 29 diagonally from above. A trailing edge 27a of the original carrying-in path 27 is positioned above the surface of the transparent platen 21 to form a step so as not to prevent the leading end of the original P from advancing.
On the other hand, a discharge tray for containing an original after reading is provided below the original tray. In order to discharge the original after reading processing into the discharge tray, a guiding member 30 for guiding the original P toward the discharge tray from the original conveying path 29 and an original guide (not shown) connecting with the guiding member 30 form an original carrying-out path 31. The surface of the guiding member 30 is made lower than the transparent platen 21 in a portion connecting with the transparent platen 21 to form with a step so as not to prevent the leading end of the original P from advancing.
FIG. 6 shows the moment of contact of the leading end of the original P with the surface of the guiding member 30. When the leading end of the original P horizontally conveyed along the original conveying path 29 is brought into contact with an inclined surface of the guiding member 30, it instantaneously receives a reaction in a direction opposite to the direction of the advance. Since the original P is pushed forward by a conveying roller (not shown) at the rear portion thereof, the original P instantaneously deflects as indicated by a two-dot and dash line in FIG. 6. During this time, image reading processing is also performed on the transparent platen 21, whereby a read image may be distorted by the deflection.
On the other hand, FIG. 7 shows the moment of passage of the trailing end of the original P through the trailing edge 27a of the original carrying-in path 27. When the trailing end of the original P passes through the trailing edge 27a of the original carrying-in path 27, the trailing end of the original P is instantaneously moved to a position indicated by a two-dot and dash line upon moving apart from the trailing edge 27a of the original carrying-in path 27. Therefore, the effect of the reaction also extends to a portion where reading processing is being currently performed, so that a read image is distorted.
That is, in the case of the image reading device, image reading processing is performed during original conveyance, whereby the read image is distorted by a subtle change in posture of the original with a slight shock received by the original during original conveyance.